Analysis on machining technology of oblique channel of valve body of forged steel stop valve

What is a forged steel globe valve?

Forged steel globe valve is mainly used for pipelines or devices with high temperature and high pressure media. It is used to connect or cut off the media in the pipeline. It is generally not used to adjust the flow. Forged steel globe valve body mostly adopts integral free forging or die forging (the channel is solid). The inlet and outlet channels of the valve body form a certain angle with the centerline of the valve body( α Angle), and the two channels are parallel to each other, and the channels at both ends are distributed above and below the sealing surface respectively. The channel angle is determined according to the flow resistance and the machining allowance between the channel and the outer circle. Making a reasonable channel processing scheme and optimizing the design of valve body channel processing mould are the basis to ensure the machining accuracy of valve body channel. The machining accuracy and quality of valve body channel directly affect the sealing performance and service life of the whole valve.

Channel processing of valve body

Process scheme

Forged steel globe valve body and its scribed benchmark as shown in Figure 1, its oblique channel generally in turning, milling, drilling, boring stations can be processed, in accordance with these four stations to develop the processing process. According to the machine table and spindle mutual position, clamping method, find the difficulty, processing efficiency and other factors specific analysis.

  • (1) Drilling processing in the valve body channel end face scribing alignment – → α angle slope tire tool positioning to find the right – → universal fixture clamping – → drilling.
  • (2) Milling processing in the valve body channel end face scribing alignment-→ α angle slope tire tool positioning to find or the milling machine spindle to α angle-→ general clamping fixture-→ milling.
  • (3) Boring processing in the valve body channel end face scribed positioning line and the outer circle of the channel scribed to find the right, review line – → according to the line to find the right (review line and boring tool feed direction center line overlap) – → general fixture clamping – → boring.
  • (4) Turning processing in the valve body channel end face scribing alignment line – → α angle slope tire tool positioning correction – → general fixture clamping – → turning.

Program analysis

(1) Drilling process
One end of the valve body channel is positioned with an inclined tire, and the other end of the channel end face is beveled. When drilling, due to the large machining allowance, the drill bit chattered and slipped under the force, and the channel machining accuracy could not be guaranteed.
20220106071124 32009 - Analysis on machining technology of oblique channel of valve body of forged steel stop valve
Figure 1 Forged steel globe valve body
(2) Milling processing
Due to the limited distance between the milling machine table and the spindle, the valve body structure is easy to cause unstable clamping and the machining range is limited when the length of the valve body is long.
(3) Boring machining
In addition to scribing the channel end positioning line, but also scribe the channel outer circle to find the right, review the line, completely rely on the scribing line to find the right positioning, subject to the influence of scribing errors, and low processing efficiency.
(4) Turning processing
Through the α angle slope tire tool to make the machine tool spindle and valve body channel parallel, and then through the scribing line to find the center line of the channel hole and the machine tool spindle coincide, find the right clamping after processing. Overcome the shortage of drilling processing accuracy, milling processing range, boring processing efficiency.
In the process of processing the forged steel globe valve channel found that there are still some disadvantages of turning processing, in the processing of the valve body oblique channel, the need to scribe the channel end face to find the line, in order to solve the problem of scribing laborious, time-consuming, the need to optimize and improve the α angle oblique tire. According to the forged steel globe valve body structure length and channel angle α, improve the design of α angle slope tire in the eccentric positioning globe (Figure 2).
20220106071243 39349 - Analysis on machining technology of oblique channel of valve body of forged steel stop valve
Figure 2 Eccentric, skew tire fixture

Structure of the positioning fixture

(1) Structure of fixture
The optimized positioning fixture consists of the tire tool, positioning screw, nut, pressure plate, spacer, T-slot screw, etc. (Fig. 3).
(2) Clamping principle
The centerline of the two channels of the valve body is parallel to the centerline of the machine tool spindle through the inclined surface of the tire tool, and then the eccentric positioning globe of the tire tool is used to fit one channel of the valve body with the eccentric globe. After the center hole of the tire tool is connected with the machine tool spindle, the center line of the channel of the valve body being processed coincides with the center line of the lathe spindle, and the workpiece obtains accurate positioning accuracy relative to the lathe and the tool to ensure the processing accuracy of the valve body channel and the quality of processing. The angle of the eccentric positioning globe on the inclined surface of the tire tool is α angle with the center hole of the tire tool. When processing the same batch of valve body, it is only necessary to mark the highest or lowest point of the valve body channel, and correspond to the thinnest or thickest point of the tire tool to find the correctness.
20220106071508 91906 - Analysis on machining technology of oblique channel of valve body of forged steel stop valve
1. flower disk 2. tire tool 3. positioning screw 4. valve body 5. nut 6. pressure plate 7. spacer 8. t-slot screw
Figure 3 Valve body machining
(3) Positioning reference
When one end of the valve body channel is mounted into the eccentric positioning globe of the tire tool, the two ends of the valve body channel are parallel to the machine tool spindle through the slope of the tire tool itself. The center hole on the tire tool is connected with the center of the spindle of the machine tool. The center hole on the tire tool is connected with the machine tool hub and spindle using the positioning screw to fix the center line of the machined channel of the valve body and the center line of the lathe spindle to determine the position of the valve body in the tire tool and the machine tool, and to ensure the accuracy of the valve body positioning relative to the tire tool.
(4) Clamping process
After positioning the workpiece, the clamping elements such as pressure plate, T-slot screw, nut, gasket and set screw clamp the tooling and the valve body so that the accurate position of the valve body after positioning will not change during the machining process and will not change in displacement or cause vibration due to the cutting force, inertia force and other forces that destroy the original positioning accuracy.

Characteristics of positioning fixture

(1) Reliable performance
The fixture positioning and clamping is accurate and reliable, and because of the large machining margin, it greatly improves the machining efficiency and safety factor in the machining process, especially in mass production, which is more obvious for the improvement of machining efficiency.
(2) Easy operation
Reduce the intensity of operation, reasonable correcting process, even if the product rework is easy to find the correct.
(3) Strong versatility
According to the characteristics of the channel angle of forged steel globe valve, the design of this inclined eccentric tire tool can be applied to the forged steel globe valve with the outer circle of the process flange, the structure length and the channel angle in line.

Conclusion

The machining process and positioning fixture of forged steel globe valve body inclined channel is applicable to various working conditions of forged steel globe valve, forged steel globe check valve, needle valve and other valve body inclined channel processing range. The positioning fixture is used for horizontal lathe manual clamping combination fixture, which is used by general-purpose fixture and special fixture to position and clamp the forged steel globe valve body to obtain the accurate position of the machined end on the machine tool. The positioning fixture is simple in structure, convenient in clamping, reliable in positioning, high in processing efficiency, good in processing quality and wide in application. It solves the problems of low efficiency of boring processing, limited range of milling processing and drilling of valve body slant channel which cannot guarantee the processing accuracy.

Author: Jiang Yaqin

Source: China Forged Steel Globe Valve Manufacturer – Yaang Pipe Industry Co., Limited (www.sfutube.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Stainless Steel Valves, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@sfutube.com

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